1. Field of the Invention
The present invention is directed to a method for operating an open 3-line type hydrodynamic coupling device, particularly a hydrodynamic torque converter.
2. Description of the Related Art
A hydrodynamic coupling device of the type mentioned above is shown in FIG. 1 and is designated generally by 10. It comprises a housing 12 having two housing shells 14, 16. The housing shell 14 is positioned in a drivetrain so as to face a drive unit and is coupled therewith by a coupling arrangement, not shown, such as a flex plate, for rotation around an axis of rotation A. The housing shell 16, which is connected in a fluid-tight manner in its radially outer area to housing shell 14, e.g., by welding, is positioned to face a gear unit and, together with impeller blades 18 supported at an inner side thereof, forms an impeller, designated generally by 20. An impeller hub 22 is provided at the radially inner area of the housing shell 16 positioned to engage in a gear unit and can be used, for example, to drive a fluid pump, e.g., an oil pump, which is provided at the latter.
A turbine 26 is arranged axially opposite the impeller 20 in an interior space 24 of the housing 12. This turbine 26 has a plurality of turbine blades 30 arranged successively in circumferential direction at a turbine shell 28. The turbine shell 28 is connected on the radially inner side to a turbine hub 32 acting as a driven member. This turbine hub 32 can be coupled via an inner toothing to a transmission input shaft for joint rotation around an axis of rotation A.
A stator 34 having stator blades 36 is located in the radially inner area axially between the impeller 20 and the turbine 24. The stator 34 has a freewheeling arrangement, designated generally by 38, which permits a rotation of the stator blades 36 around the axis of rotation A in only one rotating direction. In axial direction, the stator 34 and the freewheeling arrangement 38 thereof are supported by two pressure disks 40, 42 and respective axial bearings 44, 46 with respect to the turbine 26 and turbine hub 32 acting as driven member on one side and with respect to the housing 12 and housing shell 16 on the other side.
Further, a lockup clutch 48 is provided in the interior space 24. This lockup clutch 48 comprises an axially movable clutch piston 50 which divides the interior space 24 into a first space area 52 which also contains the turbine 26 and a second space area 54 formed substantially between the clutch piston 50 and the housing shell 14. On the radially inner side, the clutch piston 50 is supported on the turbine hub 32 in a fluid-tight manner and so as to be axially movable so that there is no fluid communication connection between the two space areas 52, 54. The torque transmission connection between the clutch piston 50 and the turbine hub 32 is carried out by a torsional vibration damper arrangement 56 whose input region is connected to the clutch piston 50 and whose output region is connected to the turbine hub 32. Damper elements which are constructed, e.g., as helical compression springs act between the input region and the output region and allow a relative rotation between the input region and output region. In this connection, it is noted that, of course, a torsional vibration damper of this kind can also act in the torque transmission path between the turbine shell 28 and the turbine hub 32, or two torsional vibration dampers can act in series and, for example, the turbine shell 28 can be connected to an intermediate region between the two torsional vibration dampers.
In the engaged state of the lockup clutch 48, the clutch piston 50 can be pressed by its radially outer region against an inner surface of the housing 12, in this case the housing shell 14. For this purpose, a friction facing can be provided, for example, at the clutch piston 50. In this connection, it is noted that the lockup clutch 48 can also have a plurality of lamellar friction elements, some of which are rotatably coupled with the clutch piston 50 and some of which are rotatably coupled with the housing 12 and which can be pressed against one another through the movement of the clutch piston 50 in the engagement direction.
In the disengaged state of the lockup clutch, the clutch piston 50 is so positioned on the radially outer side, and moved away from the housing shell 14 here, that there is communication between the two space areas 52, 54 in the radially outer region of the clutch piston 50; hence the designation “open”. To permit fluid communication between the two space areas 52, 54 also in the engaged state of the lockup clutch, i.e., when the clutch piston 50 contacts the housing shell 14 on the radially outer side, it is possible, for example, to provide a friction facing at the clutch piston 50 with grooves so that heat can also be carried away from this region of the friction facing at the same time. Alternatively or in addition, it is possible to provide one or more openings 58 in the clutch piston 50 so that fluid can flow from the first space area 52 to the second space area 54, or vice versa, corresponding to the pressure ratios adjusted in the interior space 24.
A first fluid channel area 60, which can comprise one or more openings or grooves 62 in the pressure ring 42, is provided for supplying the hydrodynamic torque converter 10 with fluid. This first fluid channel area 60 accordingly leads into an area of the interior space 24 which lies between the impeller 20 and the turbine 26.
A second fluid channel area 64 comprises, for example, one or more openings 66 in the turbine hub 32 and leads to an area of the internal space 24 that is formed substantially between the turbine 26 and the clutch piston 50. Accordingly, both the first fluid channel area 60 and second fluid channel area 64 lead into the first space area 52. As will be explained in the following, each of these fluid channel areas 60, 64 can be used to supply fluid to and/or remove fluid from the first space area 52. A third fluid channel area 68 comprises, for example, one or more openings 70 in the turbine hub 32 and leads into the second space area 54. By supplying fluid via the third channel area 70, the fluid pressure in the second space area 54 can be increased, particularly also relative to the fluid pressure in the first space area 52, in order to generate a force action loading the clutch piston 50 in the disengaging direction. If the fluid pressure in the first space area 52 is higher in relation to the fluid pressure in the second space area 54, a force action loading the clutch piston 50 in the engaging direction is generated.
By providing the first fluid channel area 60 and the second fluid channel area 64, it is possible to ensure an exchange of fluid in the first space area 52 even in the engaged state of the lockup clutch, i.e., when the clutch piston 50 contacts the radially outer side of the housing 12, in order to prevent overheating. In so doing, a fluid flow into the second space area 54 can also take place, for example, via openings 58, so that an at least smaller outflow of fluid is also possible there in the engaged state of the lockup clutch 48.
In the disengaged state of the lockup clutch, a continuous fluid communication is made possible by the supply of fluid into the second space area 54 and the possibility for this fluid to arrive in the first space area 52 at least at the radially outer side, combined with the fact that fluid is also introduced into the first space area 52, for example, via the first fluid channel area 60. This fluid can then flow off, for example, via the second fluid channel area 64.
For operation of the hydrodynamic coupling device 10, a control device is provided which ensures by generating corresponding control commands, for example, for a switching valve arrangement, that a fluid supply pressure is supplied, or is present, via the fluid supply channel or fluid supply channels intended for a respective operating state. The fluid pressure, which is generated by a fluid pump in the gear unit is used for this purpose, and the level of the fluid pressure to be supplied via a respective fluid channel area can be adjusted through correspondingly timed or pulsed control of a switching valve of this kind. Of course, the pressure ratios resulting in the internal space 24, particularly in the space areas 52, 54, also depend upon the operating state, but do not necessarily correspond to the respective fluid supply pressure in a fluid channel area.